1. Field of the Invention
The present invention relates to formylation of benzene derivatives so as to form fluorobenzaldehydes.
2. Description of the Background Art
Fluorobenzaldehydes are useful as intermediates for the synthesis of various dyes, herbicidal compounds, pharmaceuticals and the like.
There are several well-known methods for electrophilically formylating arenes which contain activating (electron-donating) substituents, but these either fail completely or are impractical for arenes which contain electron withdrawing substituents such as fluorine. Although little work has been done with alpha, alpha-dichloromethyl alkyl ethers as formylating agents, certain benzene derivatives which contain mildly activating ring substituents have previously been formylated using dichloromethyl alkyl ethers in the presence of tin chloride, titanium chloride, or aluminum chloride. Such reactions have not achieved commercial importance because the isomeric purity of the aldehyde products has been poor. Furthermore, the yields are often reduced by unwanted coupling products between the intermediates and substrate, and commercially useful quantities of dichloromethyl alkyl ethers are not readily available.
There remains a need in the art for methods of synthesizing fluorobenzaldehydes in high isomeric purity, and for new fluorobenzaldehyde compounds.